Novel Constraints on Mixed Dark-Matter Scenarios of Primordial Black Holes and WIMPs

Understand

We derive constraints on mixed dark-matter scenarios consisting of primordial black holes (PBHs) and weakly interacting massive particles (WIMPs).

• In these scenarios, we expect a density spike of the WIMPs that are gravitationally bound to the PBHs, which results in an enhanced annihilation rate and increased indirect detection prospects.
• We show that such scenarios provide strong constraints on the allowed fraction of PBHs that constitutes the dark matter, depending on the WIMP mass $m_{\chi}$ and the velocity-averaged annihilation cross-section $\langle \sigma v \rangle$.
• For the standard scenario with $m_{\chi} = 100\,{\rm GeV}$ and $\langle \sigma v \rangle = 3 \times 10^{-26}\,{\rm cm}^{3} / {\rm s}$, we derive bounds that are stronger than all existing bounds for PBHs with masses $10^{-12}\,M_{\odot} \lesssim M_{\rm BH} \lesssim 10^{4}\,M_{\odot}$, where $M_{\odot}$ is the solar mass, and mostly so by several orders of magnitude.